EXPLANATION OF PLATE XXyV. 
The figure on the left is a view of the back of the skull of Diplodocus bearing Professor Marsh’s 
No. 1922 (U.S. N. M., No. 2673). The basioccipital and the paroccipital processes of the ex- 
occipitals are broken and for the most part missing, only the articulating surface of the latter 
remaining in situ on the left side. 
The figure on the right isa view of the back of the skull bearing Professor Marsh’s No. 1921 
(U.S. N. M., No. 2672). The occipital condyle, the outline of the foramen magnum and the 
mode of the articulation of the bones forming the back of the skull is revealed more clearly in 
this specimen than in No. 2673, but there is much distortion and crushing. 
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